Impact of Swarm data on global magnetic field models

We investigate the impact of early Swarm data on global magnetic field models. Since November 2013, Swarm has been providing satellite vector magnetic data, the first since the end of the CHAMP mission over three years ago. We describe two models of the Earth's magnetic field, one of which incorporates Swarm data. Both models include data from the CHAMP and Ørsted satellites and from observatories. All data are similarly selected on the basis of local time, solar zenith angle, upstream solar wind conditions and magnetic activity. The different data are weighted according to their type, location and estimation of content of signal not being modelled. The time-varying large-scale magnetospheric field is co-estimated with the internal field. We also provide an update on efforts to collate and check ground-based observatory measurements in support of the Swarm mission. These are particularly important for bridging the gap between CHAMP and Swarm as they provide the only accurate vector observations of the magnetic field during that time.